Recently we have developed a simple, noninvasive, and safe procedure for imaging the area of damage in patients with acute myocardial infarction using technetium-99m stannous pyrophosphate (PYP). In our first 100 patients all 45 patients who had myocardial infarction by ECG and enzymes and were imaged in the first 6 days of their infarction had positive scintigrams. The objective of this proposed research is to 1) further develop this imaging technique, 2) determine the exact site and mechanism of uptake of the 99mTc-phosphates in the damaged tissue at the cellular and subcellular level using autoradiographic and elemental analysis techniques, 3) investigate why the 99mTc-phosphate localization in the infarcted tissue is time- dependent, 4) correlate histological and scintigram estimates of infarct size in experimental animals, 5) develop and test analytical techniques for measuring infarct size using the scintigrams and a typical nuclear medicine minicomputer system, 6) use the new imaging technique to determine the true incidence of myocardial infarction in patients with coronary bypass surgery and myocardial trauma, 7) study a large group of patients to clinically evaluate the technique's ability to size acute infarcts and detect extensions of acute myocardial infarctions, 8) examine patients with other forms of chest disease, specifically those with myocardial and pericardial disease, in order to determine when the scintigrams may be positive other than in acute myocardial infarction. In early detection of myocardial infarctions can result in a major reduction in the cost of health care by allowing patients without infarctions to be moved from expensive coronary care units to routine hospital beds.